# Concept of Dimensionality - PowerPoint PPT Presentation

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Concept of Dimensionality. Concept of Dimensionality (Cont.). PROCESSING GAIN = P G. Processing gain is the improvement seen by a spread spectrum system in SNR, within the system’s information bandwidth, over the SNR in the transmission channel. P G = B S / B i = R S / R i.

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Concept of Dimensionality

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### Concept of Dimensionality (Cont.)

PROCESSING GAIN = PG

Processing gain is the improvement seen by a spread spectrum system in SNR, within the system’s information bandwidth, over the SNR in the transmission channel.

PG = BS / Bi = RS / Ri

Typical PG = 20 to 60 dB

JAMMING MARGIN = MG

Jamming margin takes into account the requirement for a useful system output SNR and allow for internal losses.

MG = GP – [Lsys + (S/N)out ] , dB

Where,

Lsys = system implementation losses

(S/N)out = SNR at information, despread, output

### DIGITAL MODULATION TECHNIQUES

• Information signals (baseband signals) must be processed before transmission to be compatible with the channel

• A baseband signal modulates a high frequency carrier by varying the carrier’s phase, amplitude, or frequency

• In digital systems there are 3 basic modulation schemes:

• Phase shift keying (PSK)

• Frequency shift keying (FSK)

• In general modulated signal is of the form:

S(t) = A(t) cos [2pfo t + f(t)]